1. Field of the Invention
This invention relates to the chemical milling of metal and more particularly to the chemical milling of titanium and titanium alloys.
2. Description of the Prior Art
Prior to specifically discussing chemical milling, it is necessary to point out the manner in which it distinguishes from pickling and brightening. Chemical milling may be considered to be controlled corrosion or controlled metal removal to form sculptured metal configurations. In chemical milling, a relatively large percentage of the original metal may be rapidly removed so as to leave a minor amount of the original metal in a new configuration. As contrasted with this is pickling or scale removal whereby as much as possible of the oxide and other coatings of the metal are removed but as small amount as possible of the metal is removed. In other words, in pickling, only the surface coating of the metal is removed. In brightening or surface polishing, a minimum amount of metal is removed to form a reflective surface, as the scale has been previously removed.
Commercially-used titanium chemical milling solutions are generally a nitric-hydrofluoric acid solution. However, there is substantial room for improvement of the nitric-hydrofluoric acid solutions, in the areas of etching rate, cost, and ease of handling the materials.
Accordingly, it is the purpose of the instant invention to provide a chemical milling solution, particularly for chemical milling titanium and titanium alloys, at reduced cost which etches faster, and has greater ease of handling the components of the solution.